Dr. Bob England, director of Maricopa County Department of Public Health, says in a statement, "Measles is the most contagious disease known to man, which is why when we find one case, we must act quickly to identify additional cases and stop the outbreak as soon as possible."

The unidentified person is not vaccinated and was coming to Phoenix from Europe. Here are the public places the person visited:

According to the Centers for Disease Control, measles was "declared eliminated" from the country in 2000. The United States still averages 60 cases a year, although there were 189 cases last year.

2014 might be another big year, as there have been recent measles cases confirmed from British Columbia through California, including an entire concert crowd in Seattle that may have been exposed. One report indicates nearly 50 measles cases in California this year, the most since the disease was eradicated.

Here's more information from county health department:

Individuals who were at these locations during the above times should monitor for symptoms and call their healthcare provider if they begin exhibiting symptoms. There is no longer concern for residents visiting these public locations now

The frustration is that if enough people get just 2 doses of MMR (Measles, Mumps, and Rubella) vaccine, we would have enough immunity in the population to prevent outbreaks from happening at all. But now, again, we may watch individuals potentially get sick, lose time at work and school, and watch healthcare resources unnecessarily devoted to trying to contain this," England added.

Measles is a highly-contagious, vaccine-preventable viral illness spread through coughing, sneezing, and contact with secretions from the nose, mouth, and throat of an infected individual. Measles virus can survive in the air for hours and may be transmitted to susceptible individuals even after an infected individual no longer is in the room/area. You may be protected from measles if you were immunized for measles or if you have previously had the disease. Healthcare providers are required to report suspect cases of measles to Maricopa County Department of Public Health.